Speed regulating system



Feb. 17, 1942.

E. D. LlLJA SPEED REGULATING SYSTEM Filed June 19, 1940 fw, 04M, l

Patented Feb. 17, 1942 SPEED REGULATING SYSTEM Edgar D. Lilja, Rockford, Ill., assignor to Woodward Governor Company, Rockford, Ill., a corporation of Illinois Application June 19, 1940, Serial No. 341,264

(ci. 29o- 40) if, v w

9 Claims.

This invention relates to speed regulating systems and more particularly to governors of the type which are equipped with hydraulic compensating or stabilizing mechanism to prevent hunting.

The primary object is to modify the action of such hydraulic compensating mechanism in a novel manner such as to produce closer regulation of the prime mover speed in spite of sudden load changes.

The invention also resides in the novel and simple character of the means employed to produce the modifying action.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawing, in which Figure 1 is a schematic view and wiring diagram of a current generating system and governor control embodying the novel features of the present invention.

Figs. 2 and 3 are fragmentary views of modications.

While the invention is susceptible of various modifications and alternative constructions, I have shown in the drawing and will herein describe in detail the preferred embodiment. It is to be understood, however, that I do not intend to limit the invention by such disclosure but aim to cover all modifications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims.

In the illustrative embodiment shown in the drawing, the invention is incorporated in an hydraulic governor indicated generally at 5 for controlling the speed of a Water-wheel turbine 6 actuating a generator 'I which supplies electric current to a network 8 on which a load 9 is imposed. As usual, the turbine speed is regulated by a penstock valve I which is adjusted, usually through intermediate hydraulic mechanism (not shown), with a rod of a servomotor. Herein, the latter comprises a piston I2 mounted on the rod Il and reciprocable in a cylinder I3 and preferably urged in the speed-decreasing direction by a compression spring I4.

The governor proper comprises a head I5 carryingflyballs' I6 and driven from the turbine prime mover 6 through a connection indicated at I1. The ilyballs are urged inwardly by a. coiled spring I8 which may be adjusted through a screw I9 to vary the governor speed setting. The position of the flyballs determines the axial posi.-

tion of a pilot piston 20 with respect to a port 2| fil yservo cylinder I3 through a passage 32 connected to the port 2|.

The mechanism usually employed to compensate for the lag of the prime mover and of the control system so as to prevent hunting includes the sleeve 22 which carries a piston 33 reciprocable in a receiving cylinder 34 and urged by a spring 35 toward a neutral position. A transmitting piston 36 moves with the servo piston I2 to cause oil trapped in the lower end of the piston cylinder 31 to flow to and from the receiving cylinder 34 through a passage 38 having a leak port 39 therein adjustable by a needle 40. The valve chamber communicates with the sump 29 through a pipe 4|.

The arrangement thus far described is typical of the compensating type of hydraulic governor controls to which the present invention is particularly app.icable. In operation, an increase in the turbine speed causesthe iiyballs to move outwardly lifting the pilot piston 20 and permitting oil to es-cape to the sump from the servo cylinder through the ports 2| 'and 30 and the passages 32 and 3|. This permits the spring I4 to move the speed controller upwardly which causes closure of the valve I0 and a corresponding decrease in the turbine speed. As an incident to this movement ofthe servo and transmitter pistons l2 and 36, the pressure in the cylinders 34 and 31 is reduced permitting the piston 33 and the valve sleeve 22 to rise and follow-up the movement of the piston 20. Thus, the port 2I is covered slightly before the normal speed is again attained. Thereafter, oil from the sump 4| is drawn through the valve 39 gradually raising the compensating pressure and permitting lowering of the sleeve to normal position under the action of the centering spring 35.

In response to a decrease in speed, the piston 20 is lowered admitting high pressure fluid from the accumulator to the servo cylinder I3 so as to lower the control rod Il against the action of the spring I4 and increase the turbine speed. This results in an increase in the compensating pressure and immediate lowering of the valve sleeve 22 to close the port 2|, gradual restoration of the sleeve to normal position being effected by leakage of fluid to the sump through the valve 39.

The present invention contemplates the provision of simple means to detect sudden load changes and operates in a novel Way through the anti-hunting mechanism above described to produce a valve action anticipatory of the speed changes which would normally occur whereby to reduce the prime mover surges usually incident to sudden load changes. The supplementary compensating means includes an hydraulic actuator 42 connected in the fluid compensating circuit and operable to vary the pressure therein instantaneously in response to load changes. The actuator herein shown comprises a third cylinder 43 the head of which leads to the compensating chamber through a passage 44, the connection being to the cylinder 31 in the present instance. A piston 45 in the cylinder 43 is urged in a pressure increasing direction by a spring 46 and the piston rod 41 is connected to an electric actuator 48 the energization Vof which varies with changes in the load on the generating system. In Fig. 1, the actuator comprises an armature 49 on the piston rod coacting with a solenoid coil U which is connected to the secondary of a transformer 5| having its primary interposed in one of the lines leading from the gen erator 1 so as to be energized constantly. The spring and solenoid 'are of such construction that the piston 45 occupies a different position for each value of generator load from no load to full load and that the piston position is not inuenced appreciably by independent changes in the position of the servo piston I2. In a direct current system (see Fig. 2), a shunt 5I is interposed in one of the supply lines, the voltage across the shunt being impressed on the solenoid.

Assuming the parts to be in equilibrium, as shown in Fig. 1, the load compensating control produces its anticipating corrective action in the following manner in response to a sudden increase in load. This results in a corresponding increase in the current energizing the solenoid coil 50 drawing the plunger 49 downwardly against the compression of the spring 46. Such movement of the piston 45 draws oil out of the transmitting cylinder 31 and the consequent lowering of the pressure in the receiving cylinder 34 permits the valve sleeve 22 to rise relative to the valve piston 20. Pressure fluid thus flows from the accumulator into the power cylinder I3 and the servo piston I2 moves downwardly so as to start increasing the speed of the prime mover before the ily-balls have detected a drop in speed.

The reverse action occurs upon a sudden decrease in load which causes the pull of the solenoid 50 to be decreased and the piston 45 to move upwardly under the action oi the spring 46. Oil is thus forced into the compensating system and the piston 33 is forced downwardly so as to permit the passage of oil from the power cylinder I3 to the sump. The spring I4 then moves the control rod Il in the speed-decreasing direction in` anticipation of the speed change tha*l would normally result from the load reduction.

It will be observed that the load compensator produces the same action of the governor pilot valve as the nyballs would produce in the ab-A sence of the load detector. This action occurs in advance of the time that the ilyball action would otherwise occur and therefore is of anticipatory character so as to compensate for the inherent lag in the response of the governor and reduce surges of the prime mover that normally take place under sudden load changes. The load compensator in eifect supplements the regular governor control which operates in the normal way to correct for gradual speed changes. Owing to the leakage through the valve 38 following the pressure changes instituted by the electric load change detector, the action of the latter is of temporary character and does not produce a permanent shift in the control point of the governor.

The load compensating mechanism described above is also provided with means for adjusting the amount of compensation. To this end, a rheostat 53 is connected in parallel with the secondary of transformer 5i or, in the case of the DC system, in series with the solenoid. By adjustment of this rheostat, the change in energization of the electric actuator 48 for a given load change may be varied as desired. By opening a switch 54, the load compensator may be disabled completely.

As shown in Fig. 3, the electric load compensating actuator may take the form of a torque motor 55 geared to rack teeth on the piston rod 41, preferably through the medium of a worm- 56 on the motor shaft meshing with a worm wheel 51 on the pinion wheel. A spring 58 acts on the motor shaft in opposition to the motor. As before, a decrease in the load current decreases the motor torque permitting the piston to move upwardly and assume a different position for each load condition. For some installations, this modification is advantageous since it facilitates the addition of inertia which may be proportioned to delay the load compensating action to suit given operating conditions and prime mover characteristics. Also, the Worm gearing is self-locking so that the motor is not influenced by pressure changes in the cylinder 43 `due to independent movements of the servo piston.

It will be observed from the foregoing that the load compensating action is effected hydraulically through the intermediary of the compensating mechanism regularly employed to prevent hunting. In this way, the mechanism required to effect the anticipating adjustment is extremely simple in construction, reliable in operation, and readily adaptable to a given installation.

I claim as my invention:

l. A system for regulating the speed of a prime mover driving an electric generator having, in combination, an hydraulic servo motor regulating the speed of said prime mover, a source of pressure uid, a pilot valve controlling the flow of said fluid to and from said servo motor and including two axially movable valve elements. ilyballs driven in unison with said prime mover and modulating one of said valve elements in accordance with speed changes, interconnected cylinders filled with fluid and connected to a body of fluid through a leak valve. a transmitting piston in one of said cylinders actuated by said servo motor, a receiving piston in the other cylinder connected to said other valve element to produce a compensating action, a third iiuid filled cylinder communicating with said first mentioned cylinders and having a piston urged in a. direction to vary the pressure in the cylinders, and an electric actuator constantly but variably energized from the network supplied by said generator and controlling the position of said third piston in accordance with lcad variations.

2. A system for regulating the speed of a prime mover driving an electric generator having, in combination, an hydraulic servo motor regulating the speed of said prime mover, a source of pressure fluid, a pilot valve controlling the iiow of said iluid to and from said servo motor and including two axially movable valve elements, means responsive to the speed of said prime mover and modulating one of said valve elements, interconnected cylinders filled with uid and connected to a iluid source through a leak valve, a transmitting piston in one of said cylinders actuated by said servo motor, a receiving piston in a second cylinder connected to said other valve element to produce a compensating action, a third fluid lled cylinder communicating with said first mentioned cylinders and having a piston urged in one direction, and an electric actuator constantly but variably energized from the network supplied by said generator and operable to cause modulation of the position of said third piston in accordance with load varia- 3. The combination with a prime mover and an electric generator driven thereby of, an hydraulic governor operable in unison with said prime mover and having'a speed responsive servo motor modulating the speed of said prime mover, hydraulic compensating mechanism energized'in response to operation of said servo motor and operable to impart a compensating adjustment to said governor whereby to prevent hunting, an electric actuator variably energized in accordance with changes in the load on said generator, and means operated by said actuator to cause variations in the hydraulic pressure in said mechanism and thereby produce a supplemental adjustment of said governor compensating for sudden load changes.

4. The combination with a prime mover and an electric generator driven thereby of, an hydraulic governor operable in unison withsaid prime mover and having a speed responsivevalve and servo motor controlled thereby and modu,

lating the speed of said prime mover, hydraulic compensating mechanism energized in response to operation of said servo motor and operable to impart a compensating adjustment to said valve whereby to prevent hunting, an electric actuator variably energized in accordance with changes in the load on said generator, and means operated valve and servomotor modulating the speed of said prime mover, hydraulically connected transmitting and receiving cylinders having a leak valve outlet and pistons therein respectively connected to said servomotor and said valve so as to impart a compensating adjustment to said valve as an incident to speed adjustment of said prime mover, actuator variably energized in accordance with changes in the load on said prime mover, and a third. cylinder communicating with said cylinders and having a piston variably positioned by said actuator.

6. The combination with a prime mover and an electric generator driven thereby of, a governor driven in unison with said prime mover and operable to modulate the speed thereof, hydraulic mechanism associated with said governor to impart a compensating adjustment thereto and prevent hunting, an electric actuator variably energized in accordance with changes in the loadon said generator, means operated by said actuator to vary the hydraulic pressure in said mechanism, and means for varying the degree of energization of said actuator in accordance with the load on the generator.

7. The combination with a prime mover of a governor operable inunison with and controlling the speed of said prime mover, an hydraulic system associated with said governor to produce a compensating actionin response to speed adjust'- ments, and means operable in response to changes in the load on said prime mover to produce corresponding pressure changes in said -hydraulic system.

8. The combination with a prime mover of a governor operable in unison with and controlling the speed of said prime mover, an hydraulic system associated -with said governor to produce a compensating action in response to speed adjustments, an hydraulic cylinder communicating with said hydraulic system andhaving a piston thereinconstantly yurged in one direction, and

by said actuator to vary the hydraulic pressure` said prime mover and having a speed responsive means operable automatically to vary the position of said piston in accordance with load changes imposed on said prime mover.

9. The combination with a prime 'mover oi a governor operable in unison with and controlling the speed of said prime mover, an hydraulic system associated with said governor to produce a compensating action in response to speed changes, an hydraulic cylinder communicating with said hydraulic system and having a pistontherein constantly urged in one direction, and means op-` posing. the movement of said piston including an electric actuator constantly energized to a degree corresponding' to the load imposed on said prime mover,

. EDGAR D. LILJA. 

